On the road to the perfect fender

“We will always be aiming for the perfect fender system for the Fast Crew Supplier (FCS) 2610,” comments Damen Project Engineer Kees van Oosten. With 40 FCS 2610s built since June 2011, the model is undoubtedly one of Damen’s recent success stories. Damen, however, is always striving to push the boundaries of quality and for the last 3 years, the company’s R&D team has been working to reach this goal. “We knew that the crew transfer system of the FCS 2610 would be the bottleneck,” explains Mr Van Oosten. “We needed a fender system to improve that aspect. One that dissipates a high amount of kinetic energy and then enables the vessel to hold its position. The fender must also give feedback to the captain about his actions to maintain safety and avoid damage. All this while maintaining onboard comfort.”

Damen has carried out research, collecting data concerning a wealth of variables at the BARD Offshore 1 wind farm in German North Sea waters. BARD 1 is renowned for its harsh conditions including high waves with short wavelengths. “This is real life testing,” says Damen Design and Proposal Engineer Brian Mewis. “We are testing fenders because the market cannot deliver what we are asking. The whole market is in a trial-anderror phase and our aim is to narrow down the options to the optimum end result.”

The team continues scaled-down testing under controlled conditions at Damen’s yard in Gorinchem, the Netherlands. By being able to control all the variables they can gain valuable insight into various fender dimensions and foam densities. “We have the knowledge and we listen to the feedback from customers,” continues Mr Mewis. “Our customers need to have a higher operability in rougher seas with less downtime.”

By working together with customers and fender manufacturers, Damen is making progressive steps in fender development. “We are on the road to the perfect fender system,” concludes Damen Business Development Manager Offshore Wind Peter Robert. “A system that further improves the already high performance of the FCS 2610.”

Absorbing Forces

When a FCS 2610 makes contact with an offshore wind turbine there are both horizontal and vertical forces involved. “Energy absorption is just one of the purposes of a FCS 2610 fender,” explains Damen Design Engineer Brian Mewis. “These are the horizontal forces.”

Absorbing these forces prevents structural damage to turbine and vessel. “The fender also has to keep the vessel in place against the wind turbine so that the bow of the vessel ‘sticks’ to the structure, preventing vertical movement of the bow so that the maintenance engineer can transfer safely.” This is achieved by the vessel maintaining forward propulsion – the stern, meanwhile, moves up and down with wave action. The energy from the horizontal impact is absorbed by a foam core and vertical movement is prevented by a polyurethane outer layer that provides friction. “The challenge is to combine the two demands of vertical and horizontal forces.”